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| <h5 class="subsubsection">3.6.2.3 Flonums</h5> |
| |
| <p><a name="index-flonums-181"></a><a name="index-floating-point-numbers-182"></a><a name="index-constants_002c-floating-point-183"></a> |
| <a name="index-precision_002c-floating-point-184"></a>A <dfn>flonum</dfn> represents a floating point number. The translation is |
| indirect: a decimal floating point number from the text is converted by |
| <samp><span class="command">as</span></samp> to a generic binary floating point number of more than |
| sufficient precision. This generic floating point number is converted |
| to a particular computer's floating point format (or formats) by a |
| portion of <samp><span class="command">as</span></samp> specialized to that computer. |
| |
| <p>A flonum is written by writing (in order) |
| <ul> |
| <li>The digit ‘<samp><span class="samp">0</span></samp>’. |
| (‘<samp><span class="samp">0</span></samp>’ is optional on the HPPA.) |
| |
| <li>A letter, to tell <samp><span class="command">as</span></samp> the rest of the number is a flonum. |
| <kbd>e</kbd> is recommended. Case is not important. |
| |
| <p>On the H8/300, Renesas / SuperH SH, |
| and AMD 29K architectures, the letter must be |
| one of the letters ‘<samp><span class="samp">DFPRSX</span></samp>’ (in upper or lower case). |
| |
| <p>On the ARC, the letter must be one of the letters ‘<samp><span class="samp">DFRS</span></samp>’ |
| (in upper or lower case). |
| |
| <p>On the Intel 960 architecture, the letter must be |
| one of the letters ‘<samp><span class="samp">DFT</span></samp>’ (in upper or lower case). |
| |
| <p>On the HPPA architecture, the letter must be ‘<samp><span class="samp">E</span></samp>’ (upper case only). |
| |
| <li>An optional sign: either ‘<samp><span class="samp">+</span></samp>’ or ‘<samp><span class="samp">-</span></samp>’. |
| |
| <li>An optional <dfn>integer part</dfn>: zero or more decimal digits. |
| |
| <li>An optional <dfn>fractional part</dfn>: ‘<samp><span class="samp">.</span></samp>’ followed by zero |
| or more decimal digits. |
| |
| <li>An optional exponent, consisting of: |
| |
| <ul> |
| <li>An ‘<samp><span class="samp">E</span></samp>’ or ‘<samp><span class="samp">e</span></samp>’. |
| <!-- I can't find a config where "EXP_CHARS" is other than 'eE', but in --> |
| <!-- principle this can perfectly well be different on different targets. --> |
| <li>Optional sign: either ‘<samp><span class="samp">+</span></samp>’ or ‘<samp><span class="samp">-</span></samp>’. |
| <li>One or more decimal digits. |
| </ul> |
| |
| </ul> |
| |
| <p>At least one of the integer part or the fractional part must be |
| present. The floating point number has the usual base-10 value. |
| |
| <p><samp><span class="command">as</span></samp> does all processing using integers. Flonums are computed |
| independently of any floating point hardware in the computer running |
| <samp><span class="command">as</span></samp>. |
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